The OS1OOOA general purpose oscilloscope is a solid state, portable, dual trace oscilloscope suitable for a diverse number of laboratory and television applications. DC mode bandwidth at the -3 dB points is DC to 20 MHz, and AC mode bandwidth is 2 Hz to 20 MHz. Sensitivity from 5 mV/cm to 20V/cm is covered in 12 switched ranges with a common variable overlap control effective on all ranges. The sensitivity can be increased to 1 mV/cm by connecting the Y1 and Y2 channels in cascade. Several display modes are incorporated: Yl or Y2 single trace; Yl and Y2 dual trace with alternate sweep or 250 kHz chopped and automatically selected by the setting of the timebase switch; X - Y in which the precision attenuators in one Y channel are utilised to control the amplitude of the X signal. Yi +Y2 (algebraic addition) or Yj—Y2 facilities are also available. Sweep speeds from ls/cm to 0.5 ßs/cm are covered in 20 switched ranges with a common variable overlap control effective on all ranges. A XI0 facility is incorporated so that the sweep speed can be increased to 50 ns/cm. Switch selected trigger sources are, internal from either one of the two Y channels, external via a front-panel connector, and the AC supply. A facility for triggering from television signals is also incorporated. Level control may be effected manually or automatically. In the absence of trigger signals in the ‘Auto’ mode, the time-base switches to an automatic free run condition and produces a bright line trace.